At the beginning of“The Narrow Door,” Paul Lisicky’s new memoir, we learn that Denise Gess, his closest friend of more than two decades, has recently died of cancer. This memoir, then, is “the book that wants to bring back my friend.”

The friendship Lisicky conjures is a relationship in the fullest sense — intoxicating, brutal, draining and sustaining. Paul and Denise meet as teaching assistants at Rutgers University in 1983 — Denise is a writer on the verge of fame; Paul is just starting out. Denise, a divorced mother, is ready to have extravagant affairs with famous writers, while Paul is living with his parents and waiting to come out as gay.

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“Listening to Denise is my real education,” Lisicky writes, describing their hours-long daily phone conversations about writing and thinking and dreaming and failing and yearning that take precedence over all else. If the romance of this relationship isn’t sexual, it’s romance nonetheless: “Our love for each other comes first,” Lisicky writes, when faced with Gess’ competitive streak.

Lisicky dispenses with linear expectations of memoir, and offers a book structured instead by feeling. This is, after all, how memory works. Chapters shift back and forth across decades, dispensing with a tidy timeline.

If “The Narrow Door” is centrally about Lisicky’s relationship with Gess, it’s also about the collapse of his long-term relationship with poet Mark Doty (referred to in the book only as “M”). They’ve been together for 15 years — they talk for hours about writing; they finish each other’s sentences; they even wear the same size shoes. Their relationship has always been open, but this has meant living together, and having anonymous sex on the side — never “an overnight stay, and certainly not a boyfriend.” When M starts to date someone else, the relationship dissolves. Lisicky writes:

To think of love as a laser beam of attention. To think you

could beam that attention toward him in such a way he

wouldn’t even know you were doing it. To learn that your

attention is doomed. Unwelcome, better having been put

to other uses.

This description of love and its disappointments could also apply to Denise. Watching her at a reading several years after her career has stalled, Lisicky notices the way she ignores him, instead courting straight men who might help her career. “Am I jealous?” he asks. “Maybe not so much jealous as confused. But to bear witness to the theater of power and exclusion? Well, I’d rather not be a part of that.”

While “The Narrow Door” doesn’t exactly bear witness to the theater of power and exclusion, the lives Lisicky describes — his own, Denise’s, and by inference M’s as well, are certainly marked by striving. When Lisicky describes his first stay at a writers retreat in 1986, he is putting as much effort as possible into “impersonating the look of the successful young writer of the day.”

And his life with M — one that includes a condo in downtown Manhattan, and a second home in the Hamptons — certainly fits the rarefied image of writers of a certain class. So it’s something of a shock, upon the looming demise of Lisicky’s relationship with M, when he reveals: “I have nothing: no house, no furniture, no permanent job, just a couple thousand dollars in the bank.”

“I might as well be twenty-three years old again,” Lisicky declares. (He’s in his early 50s at the time.) But this moment of financial vulnerability (and potential self-realization) is not revisited. “The Narrow Door” is meticulous in its description of grief and loss, and never shies from the full complexity and range of emotion in Lisicky’s relationship with Gess. And yet, there’s a sense that Lisicky is holding back when it comes to his relationship with M — there’s something missing.

But perhaps this is what a relationship feels like when it’s gone on too long. “I don’t think you know how to break up,” M says to Lisicky, but could anyone really know how to gracefully exit a relationship of 15 years? “I’ve never made my map,” Lisicky writes. “I’ve looked at the plan handed to me; I’ve looked to see how I can make room inside that plan.”

“The Narrow Door” is this map — the lines meander and they are distinct. The book ends as it begins: with Denise’s death. “We’re watching her face. It’s a little like waiting for a movie to start.”

Mattilda Bernstein Sycamore is most recently the author of “The End of San Francisco.” E-mail: books@sfchronicle.com